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PREFERRED FIDUCIAL ALIGNMENT
Alignment within the fiducial marks provides a rapid, visual indication of proper device alignment.
Best Workmanship Practice
PREFERRED
Solder terminations are smooth and rounded, with a clearly defined boundary. Terminations exhibit no voids, and are of the same diameter, volume, darkness and contrast. Registration is straight, with no pad overhang or rotation. No solder balls are present.
ACCEPTABLE VOIDS
Terminations that exhibit less than 10% voiding in the ball-to-board interface are acceptable.
Best Workmanship Practice
Page:
1
Revision Date:
Section:
7.13
Revision:
Book:
7
Released:
06.27.2002
ACCEPTABLE PAD OVERHANG
Pad overhang is less than 25%.
Best Workmanship Practice
NASA WORKMANSHIP STANDARDS
Page:
3
Revision Date:
Section:
7.13
Revision:
Book:
7
Released:
06.27.2002
SURFACE MOUNT TECHNOLOGY (SMT) BALL GRID ARRAY - BGA
BALL GRID ARRAY - BGA Ball Grid Array packages were designed to provide a device having high density input/output (I/O) array pattern interconnects, while minimizing device footprint and temperature coefficient (TC) problems. The array design features a low profile with shorter interconnections – resulting in superior electrical performance, speed, heat dissipation and noise reduction. The placement of the interconnects on the bottom of the package limits visual inspection of the inner terminations, requiring the use of special microscopes or three-dimensional X-ray.
UNACCEPTABLE NON-REFLOW
Lack of proper reflow indicates poor process controls, typically insufficient heat during reflow.
Best Workmanship Practice
UNACCEPTABLE NON-WETTING
Non-wetting is an indicator of poor process controls.
Best Workmanship Practice
UNACCEPTABLE POOR DEFINITION
Solder joint boundaries exhibiting poor definition, appear fuzzy, or which blend in with the background, indicate insufficient reflow.
Best Workmanship Practice
UNACCEPTABLE SOLDER BALLS
Solder ball(s) that violate the minimum electrical clearance shall be cause for rejection.
Best Workmanship Practice
UNACCEPTABLE SOLDER BALLS
Solder balls that bridge more than 25% of the distance between the leads shall be cause for rejection.
Best Workmanship Practice
UNACCEPTABLE SOLDER BRIDGE
Solder bridging is an indicator of improper process, typically excess paste deposit.
Best Workmanship Practice
NASA WORKMANSHIP STANDARDS
SURFACE MOUNT TECHNOLOGY (SMT) BALL GRID ARRAY – BGA (cont.)
Section:
7.13
Revision:
Revision:
Page:
4
Revision Date:
Book:
7
Released:
06.27.2002
Page:
2
Revision Date:
Book:
7
Released:
06.27.2002
SURFACE MOUNT TECHNOLOGY (SMT) BALL GRID ARRAY – BGA (cont.)
Section:
7.13
UNACCEPTABLE POOR FLOW
The fillet shall not exhibit poor or uneven flow at the top of the solder fillet.
Best Workmanship Practice
NASA WORKMANSHIP STANDARDS
UNACCEPTABLE SOLDER OPENS
Solder opens are an indicator of improper process, typically insufficient paste deposit.
Best Workmanship Practice
UNACCEPTABLE VOIDING
Terminations that exhibit 10% (or more) voiding in the ball-to-board interface shall be grounds for rejection.
Best Workmanship Practice
UNACCEPTABLE DARK SPOTS
Dark spots in the x-ray view, which cannot be attributed to circuitry (traces) or components underneath the BGA, shall be cause for rejection.
Best Workmanship Practice
UNACCEPTABLE EXCESSIVE PAD OVERHANG
Pad overhang shall not exceed 25%.
Best Workmanship Practice
UNACCEPTABLE FRACTURE
Terminations exhibiting fractures in the ball-to board interface are unacceptable.
Best Workmanship Practice
UNACCEPTABLE MISALIGNMENT
Misalignment is an indicator of improper process controls.
Best Workmanship Practice
UNACCEPTABLE MISSING BALL
BGAs exhibiting missing solder balls shall be rejected.
Best Workmanship Practice
UNACCEPTABLE MISSING SOLDER
Missing solder is an indicator of improper process controls.
Best Workmanship Practice
NASA WORKMANSHIP STANDARDS
SURFACE MOUNT TECHNOLOGY (SMT) BALL GRID ARRAY – BGA (cont.)